Horizontal pumping systems are used in various industries for a variety of purposes. In many cases, a multistage vertical turbine pump is horizontally mounted on a skid-supported frame and used in a horizontal orientation. For example, in the oil and gas industry horizontal pumping systems are used to pump fluids, such as water separated from oil, to a remote destination, such as a tank or disposal well. Typically these horizontal pumping systems include a pump, a motor, and a suction housing positioned between the pump and the motor. A thrust chamber is also included between the motor and the suction housing. The pump includes a discharge assembly that is connected to downstream piping.
In downhole pumping applications, the pressure of the fluid at the pump inlet is often increased by head pressure created by the column of fluid in the wellbore. In surface-based pumping systems, however, the net positive suction head available (NPSHA) may be much lower. To match the NPSHA to the suction pressure required by the pump (NPSHR), designers have used a separate boost pump that charges the fluid to a NPSHA that matches or exceeds the NPSHR required by the horizontal pump. The use of a separate boost pump is expensive and requires additional space that may not be available in certain applications.
To overcome the inefficiencies of using a separate boost pump, designers have also tried to incorporate a low NPSH stage within the multistage centrifugal pump housing. Although more convenient than an external boost pump, placing a low NPSH stage within the pump housing restricts the diameter of the NPSH stage. Additionally, because the internal NPSH stage will typically be longer than a standard stage, the balance of the components within the multistage pump must be modified to accommodate the NPSH stage. The additional design and manufacturing efforts required to incorporate an NPSH stage within the pump housing increases lead times and costs. There is, therefore, a need for a cost-effective solution for boosting the NPSH on a horizontal pumping system.